ANN ARBOR, Mich.California's San Andreas fault is notorious for repeatedly generating major earthquakes and for being on the brink of producing the next "big one" in a heavily populated area. But the famously violent fault also has quieter sections, where rocks easily slide against each other without giving rise to damaging quakes.

The relatively smooth movement, called creep, happens because the fault creates its own lubricants?slippery clays that form ultra-thin coatings on rock fragments, geologist Ben van der Pluijm and colleagues at the University of Michigan and Germany's Ernst-Moritz-Arndt Universit